In OFDM (Orthogonal Frequency-Division Multiplexing) communications, an input signal is applied a subcarrier modulation and an IFFT (Inverse Fast Fourier Transformation) to generate a baseband signal. Thus, the OFDM communication is characterized in that an increase in the number of subcarriers and in FFT (Fast Fourier Transformation) size results in a baseband signal with a large peak and increases PAPR (Peak-to-Average Power Ratio). The increased PAPR leads to the need for an amplifier having linearity over a wide range in order to transmit signals without distortion. Therefore, a technique for reducing PAPR has been developed.
In order to reduce PAPR, a technique described in Unexamined Japanese Patent Application Kokai Publication No. 2006-165781 controls the phase of a subcarrier modulation signal based on an optimal phase calculated in a sequential decision procedure before performing an IFFT.